Effect of aging temperature on phase decomposition and mechanical properties in cast duplex stainless steels

The microstructure and mechanical properties in unaged and thermally aged (at 280°C, 320°C, 360°C, and 400°C to 4300h) CF–3 and CF–8 cast duplex stainless steels (CDSS) are investigated. The unaged CF–8 steel has Cr-rich M23C6 carbides located at the δ–ferrite/γ–austenite heterophase interfaces that...

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Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2017-04, Vol.690 (C), p.365-377
Main Authors: Mburu, Sarah, Kolli, R. Prakash, Perea, Daniel E., Schwarm, Samuel C., Eaton, Arielle, Liu, Jia, Patel, Shiv, Bartrand, Jonah, Ankem, Sreeramamurthy
Format: Article
Language:English
Subjects:
Atom probe tomography
Carbides
Decomposition
Delta ferrite
Duplex stainless steel
Duplex stainless steels
G–phase
M23C6 carbide
MATERIALS SCIENCE
Mechanical properties
Microstructure
Phase decomposition
Precipitates
Spinodal decomposition
Stainless steel
Tomography
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Summary:The microstructure and mechanical properties in unaged and thermally aged (at 280°C, 320°C, 360°C, and 400°C to 4300h) CF–3 and CF–8 cast duplex stainless steels (CDSS) are investigated. The unaged CF–8 steel has Cr-rich M23C6 carbides located at the δ–ferrite/γ–austenite heterophase interfaces that were not observed in the CF–3 steel and this corresponds to a difference in mechanical properties. Both unaged steels exhibit incipient spinodal decomposition into Fe-rich α–domains and Cr-rich α’–domains. During aging, spinodal decomposition progresses and the mean wavelength (MW) and mean amplitude (MA) of the compositional fluctuations increase as a function of aging temperature. Additionally, G–phase precipitates form between the spinodal decomposition domains in CF–3 at 360°C and 400°C and in CF–8 at 400°C. The microstructural evolution is correlated to changes in mechanical properties. Understanding relationships between microstructure and mechanical behavior in cast duplex stainless steels across multiple length scales. [Display omitted]
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2017.03.011